1,721,573 research outputs found
The cost of being bright
No full textMale ornaments are predicted to be a signal of the genetic quality of a male but often the relationship between ornaments and the physiological performances of males is unclear. Males of Metichnogaster cillipennis, a hover-wasp, during their courtship flights send luminous signals to females by using two abdominal reflectors. Malpighian tubules, an essential organ in the physiology of insects, participate in the building of the larger of these reflectors but at a physiological cost. By evaluating the capacity of light reflection from males during their courtship, females can assess directly the physiological quality of males. © 2008 Springer Science+Business Media, LLC
The role of hERG1 ion channels in epithelial-mesenchymal transition and the capacity of riluzole to reduce cisplatin resistance in colorectal cancer cells
No full textPurpose: The transition of cells from the epithelial to the mesenchymal state (EMT) plays an important role in tumor progression. EMT allows cells to acquire mobility, stem-like behavior and resistance to apoptosis and drug treatment. These features turn EMT into a central process in tumor biology. Ion channels are attractive targets for the treatment of cancer since they play critical roles in controlling a wide range of physiological processes that are frequently deregulated in cancer. Here, we investigated the role of ether-a-go-go-related 1 (hERG1) ion channels in the EMT of colorectal cancer cells. Methods: We studied the epithelial-mesenchymal profile of different colorectal cancer-derived cell lines and the expression of hERG1 potassium channels in these cell lines using real-time PCR. Next, we knocked down hERG1 expression in HCT116 cells using lentivirus mediated RNA interference and characterized the hERG1 silenced cells in vitro and in vivo. Finally, we investigated the capacity of riluzole, an ion channel-modulating drug used in humans to treat amyotrophic lateral sclerosis, to reduce the resistance of the respective colorectal cancer cells to the chemotherapeutic drug cisplatin. Results: We found that of the colorectal cancer-derived cell lines tested, HCT116 showed the highest mesenchymal profile and a high hERG1 expression. Subsequent hERG1 expression knockdown induced a change in cell morphology, which was accompanied by a reduction in the proliferative and tumorigenic capacities of the cells. Notably, we found that hERG1expression knockdown elicited a reversion of the EMT profile in HCT116 cells with a reacquisition of the epithelial-like profile. We also found that riluzole increased the sensitivity of HCT116 cisplatin-resistant cells to cisplatin. Conclusions: Our data indicate that hERG1 plays a role in the EMT of colorectal cancer cells and that its knockdown reduces the proliferative and tumorigenic capacities of these cells. In addition, we conclude that riluzole may be used in combination with cisplatin to reduce chemo-resistance in colorectal cancer cells
Quantitative high-throughput analysis of synthetic genetic interactions in Caenorhabditis elegans by RNA interference
No full textAbstractBiological processes are highly dynamic but the current representation of molecular networks is static and largely qualitative. To investigate the dynamic property of genetic networks, a novel quantitative high-throughput method based on RNA interference and capable of calculating the relevance of each interaction, was developed. With this approach, it will be possible to identify not only the components of a network, but also to investigate quantitatively how network and biological processes react to perturbations. As a first application of this method, the genetic interactions of a weak loss-of-function mutation in the gene efl-1/E2F with all the genes of chromosome III were investigated during embryonic development of Caenorhabditis elegans. Fifteen synthetic genetic interactions of efl-1/E2F with the genes of chromosome III were detected, measured and ranked by statistical relevance
Laser Welding of Thin Copper and Aluminum Sheets: Feasibility and Challenges in Continuous-Wave Welding of Dissimilar Metals
No full textThe present paper defines process windows for laser welding of thin copper and
aluminum sheets in Al-Cu and Cu-Al lap-joint configurations, exploiting different
process strategies and parameters. A single-mode continuous-wave (CW) laser source
was exploited with both linear and wobbling strategies. In both cases the influence of
several parameters, such as, laser power, spot dimensions and scanning speed on the
resulting microstructure and joint strength was analyzed. The influence of one, two and
three parallel beads on the maximum shear strength was also evaluated. The optimum
process configurationswere finally determined based onmaximum joint strength in shear
tests and the mixing of the two parent metals occurring after welding was determined by
means of SEM-EDS analysis
Stiffness prediction and deformation analysis of Cobalt-Chromium lattice structures: From periodic to functionally graded structures produced by additive manufacturing
Full text linkLattice structures are candidates for innovative design of orthopedic implants and other highly functional products. In particular, functionally graded structures can be employed to achieve the required strength and stiffness for optimal stress-strain distribution. Prediction of the real behavior of these structures is essential for effective design. In the present work, stiffness prediction and deformation analysis of Cobalt-Chromium lattice structures manufactured using laser-based Powder Bed Fusion additive manufacturing were carried out. The study was developed in two steps: compressive tests and Digital Image Correlation were performed on periodic structures, with the results used to predict the stiffness of two types of functionally graded structures. The proposed method was validated experimentally, with the predicted stiffness of structures designed with the proposed elementary units within 6.1% for all tested cases. An array of stiffness data was then defined to allow free design of graded structures foreseeing specific compressive properties. The mechanical properties and deformation behavior of the structures were also investigated, with the local strain distribution mapped and compared to global deformation values
Additive manufacturing of AISI 420 stainless steel: process validation, defect analysis and mechanical characterization in different process and post-process conditions
Full text linkStainless steel (SS) alloys produced by laser-based powder bed fusion (LPBF) offers comparable and sometime superior mechanical properties compared to conventionally processed materials. Some of these steels have been extensively studied over the last decade; however additively manufactured martensitic SS, such as AISI 420, need further research in characterizing their post-built quality and mechanical behaviour. This lack of information on martensitic SS is not consistent with their growing demand in the automotive, medical and aerospace industries due to their good corrosion resistance, high hardness and good tensile properties. Selection of the appropriate process parameters and post treatments plays a fundamental role in determining final properties. For this reason, the effect of LPBF process parameters and different heat treatments on density, defect characteristics and locations, roughness and mechanical properties of AISI 420 were investigated in this paper. A first experimental campaign was carried out to establish a set of suitable process parameters for industrial applications. Starting from this result, detected defect properties were investigated by computed tomography (CT) scans. Dimensions, sphericity and distributions of defects inside the volume were analysed and compared between samples manufactured with different parameters. In the second part of the paper, the influence of process and post-process conditions on mechanical properties was investigated. The final presented results establish a correlation between the employed production cycle and the resulting properties of LPBF AISI 420 specimens
Social feeding behavior of Trichoplax adhaerens
No full textAnimals have evolved different foraging strategies in which some animals forage independently and others forage in groups. The evolution of social feeding does not necessarily require cooperation, social feeding can be a beneficial individual-level strategy if it provides mutualistic benefits, for example though increasing the efficiency of resource extraction or processing. We found that Trichoplax adhaerens, the simplest multicellular animal ever described, engages in social feeding behavior. T. adhaerens lacks muscle tissue, nervous and digestive systems-yet is capable of aggregating and forming groups of closely connected individuals who collectively feed. The tight physical interactions between the animals are transitory and appear to serve the goal of staying connected to neighbors during the external digestion of algae when enzymes are released on the biofilm and nutrients are absorbed through the ventral epithelium. We found that T. adhaerens are more likely to engage in social feeding when the concentrations of algae are high-both in a semi-natural conditions and in vitro. It is surprising that T. adhaerens-an organism without a nervous system-is able to engage in this social feeding behavior. Whether this behavior is cooperative is still an open question. Nevertheless, the social feeding behavior of T. adhaerens, an early multicellular animal, suggests that sociality may have played an important role in the early evolution of animals. It also suggests that T. adhaerens could be used as a simple model organism for exploring questions regarding ecology and sociobiology
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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